Beyond smell, many odorants stimulate the trigeminal nerve, which provides the facial component of chemesthesis, the perception of sensations originating from chemicals, often takes taking the form of irritation. Using human volunteers, some of whom have no sense of smell (anosmia), we have been and wish to continue intranasal chemesthesis and its interactions with olfaction. The project proposes three broad goals. Specific Aim 1 will investigate whether anosmics are sensitive to a range of chemesthetic stimuli relative to normosmics, in whom the sense of smell is fully functional. Should anosmics have an associated diminution in sensitivity to chemical irritants, they and their physicians should be made aware of this potentially dangerous situation. Specific Aim 2 will investigate quality coding in intranasal chemesthesis by testing a variety of chemesthetic agents in normosmics and anosmics. If quality coding exists within chemesthesis, then information would be needed to determine how many qualities exist, how the perception of these qualities influence each other and how they interact with olfaction. Specific Aim 3 will explore interaction between chemesthesis and olfaction by determining the effects of exposure to and adaptation of intranasal chemesthesis on olfactory sensitivity and vice versa. At present there is some confusion about the interaction between intranasal chemesthesis and olfaction. Work in this specific aim will collect additional data on this issue which should provide for a greater understanding of olfactory and chemesthetic interactions. To these ends, we will rely upon the ability of people to adapt to stimuli and to determine which side of the nose is being stimulated when an irritant activates the trigeminal nerve unilaterally (unlikely as it may seem, olfaction per se does not provide such information). In other work we willy rely upon the qualities of the stimuli to provide cues that individuals can use to discriminate between alternative choices. Results should contribute to an overall understanding of how individuals interact with their ever-expanding chemosensory environment.